There are various types of industrial vehicles in use today, and one of the most popular of these is the skid-steer loader. A skid-steer loader is a compact, highly maneuverable vehicle in which the wheels on opposite sides of the vehicle are independently driven through hydrostatic transmissions. Maneuvering is accomplished by driving the wheels on each side of the vehicle at different speeds and/or in different directions. The operator sits in front of the engine and between the arms of a hydraulically operated boom on which a bucket, grapple fork, rake, auger or other accessory can be mounted. A cab or roll cage is usually provided about the operator's compartment for protection.
Seatbelts traditionally have been provided for restraining the operator in the vehicle during operation. Seatbelts, of course, depend upon the operator to fasten them so that they can serve their intended purpose. Accidents and injuries have occurred when operators were not wearing their seatbelts and were pitched forward. Moreover, heretofore the functions of seatbelts and control interlocks have not been interrelated.
Other than encouraging operators to wear their seatbelts, attempts have been made to develop auxiliary restraint systems and/or control interlock systems for improving safety. Such control interlock systems are especially desireable in skid-steer loaders where the operators must climb into and out of their seats from the front of the vehicles and directly over the controls. For example, the Bobcat loader available from the Melroe Division of Clark Equipment Company utilizes a pivotal seat bar. When the bar is in the up position, the foot pedals and the boom lift arms are locked and the operator can easily enter or exit the vehicle. When the seat bar is down, the controls are unlocked and the bar provides additional protection against the operator pitching forward during operation of the vehicle. This type of restraint system, however, is completely independent of the seatbelt, and does not function in any way to encourage the operator to fasten his seatbelt as well. Moreover, this type of swing down seat bar is somewhat unwieldy and expensive.
Seat-activated devices also have been utilized heretofore, however, these have certain disadvantages. For example, the skid-steer loaders from Sperry New Holland incorporate seat-activated systems which deactivate the boom hydraulics if the operator comes off the seat for any reason. Such systems are extremely sensitive to bouncing of the operator in the seat. Operation by a lightweight operator and/or over rough terrain can cause multiple cycling leading to increased wear and maintenance. Again, operation of this type system is completely independent of the seatbelt.
There is thus a need for an improved operator restraint/control lockout system of unobtrusive construction which functions to positively lockout predetermined controls of the vehicle unless the seatbelt is properly fastened.